Spaced multi-wall construction unit

ABSTRACT

A construction unit for constructing large pressure vessels such as offshore platforms and other pressure vessels which are subjected to high internal and/or external pressures wherein the construction unit comprises a multi-wall structure having a plurality of laterally spaced walls joined together at their upper and lower ends, respectively, and at their opposite sides to form an enclosure, and having a plurality of tensioning means for prestressing the construction unit prior to filling the enclosure with aggregate, concrete, grout or other suitable substantially incompressible material. The invention also includes the method of erecting off-shore vessels constructed of the spaced multi-wall construction units.

United States Patent Hayes Aug. 29, 1972 [54] SPACED MULTl-WALL CONSTIUCTION UNIT Primary Examiner-Price C. Paw, Jr. 12 Inventor: Charles w. Hayes, 2334 Haidare St., Houston, Tex. 77055 [22] Filed: Feb. 9, 1970 [21] Appl. No.: 9,657

[52] US. Cl. "521233, 52/249. 52/426 [51] InLCl. ...I04h IMBMh'I/fl [58] Field at Search .521426, 425, 249, 248, 245, 521223 R, 224, 562, 424

[56] memes (led UNITED STATES PA'IEN'I'S 87,569 3/1869 2,315,894 4/1943 1,345,985 7/1920 2,319,105 5/1943 2,942,454 6/1960 Jackson ..52l249 [57] ABSTRACT A construction unit for constructing large pressure vessels such as offshore plstforms and other pressure vessels which are subjected to high internal end/or externel pressures wherein the construction unit comprises a multi-wnll structure having a plurality of laterally spaced walla joined together at their upper and lower ends, respectively, and at their opposite sides to form an enclosure, and having a plurality of tensioning means for prestressing the construction unit prior to filling the enclosure with aggregate, concrete, grout or other suitable substantially incompressible material. The invention also includes the method of erectingofi-shorevesselsconsu'uctedofthespaced rnuIti-wall construction units.

l SPACED MUL'I'l-WALL CONSTRUCTION UNIT BACKGROUND OF THE INVENTION 1. Field of the invention The present invention pertains to a spaced multi-wall construction unit for large pressure vessels such as offshore platforms and other vessels subjected to high internal and/or external pressures and to a method for erecting such vessels. I

2. Description of the Prior Art lnthepriorartpressur'evesselconstructiomtbewalls of the pressure vessel are typically made of substantially solid steel, either by forming a single thick plate of steel into a vessel or by building up a laminated or multi-layer vessel from a plurality of relatively thin plates of steel which are joined together so a to fonn a substantially continuous swel wall structure. The difficulty and expense involved in formirq large vessels of relatively thick steel plate, or of a plurality of thin layers, renders these types of construction highly impractical for forming large pre-ure vessels suitable for use at the pressures encountered in relatively deep water. in addition to the material and labor cost involved and capital equipment required for forming large steel plates, there is the additional expense of heating and reheating a plate for successive pales through the heating equipment when the veael is made of a single steel plate, the expense of radiographing and stress relieving a vessel once it is completed as well as the transportation problems inherent in handling large, very heavy steel wall vessels.

SUMMARY OF THE INVENTION The present invention comprises a spaced multi-wall construction unit comprising an inner skin and an outer skin spaced laterally apart and joined together at opposite ends by transverse plates to form a relatively lightweight enclosure with tension means connecting the inner and outer skins and transverse plates for prestressing the construction unit. The individual con struction units can be prestressed to approximately the pressures expected to be encountered in use after they have been joined together to form a vessel or other construction, after which the space between the inner and outer skins can be filled with aggregate, concrete, grout or other suitable material to form a rigid spaced multi-wall construction unit suitable for use in constructing large pressure vessels. In some applications where low pressures are encountered, such as in shallow water, the prestressed laterally spaced wall construction can be used without filling the area between the walls, if desired.

It is also an object of the present invention to provide a new and improved method for erecting a mature or vessel for use in the ocean or ofishore on the ocean bottom, comprising assembling a vessel or structure from a plurality of prefabricated construction units, each having laterally spaced inner and outer walls with means for joining the edges of such walls to form an enclosure, joining the sections together or form an assembled structure, prestressing each of such units the desired amount, floating the assembled structure to the location for erection, and filling the space between the laterally spaced walls with fine aggregate, concrete, grout or other suitable material beginning at the lower end of such assembled structure to cause the lower end tosinktotheoceantloorwiththe bottornofsuchstruc- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 isanisometricviewpartlyinsectionofanofishore drilling and production platform constructed of laterally spaced multi-wall construction units;

FIG. 2 is an sectional view showing details of the base of such oflshore platform.

FIG. 3 is a view partly in section and partly in elevation showing additional details of the base construction;

FIG. 4 is a side elevation of a portion of the construction unit with the outer skin removed showing longitudinally extending supports and tensioning means for prestressing the units; and

FIG. 5 is a sectional view taken on line 5-5 of FIG. 4 showing details of the transverse tensioning means in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the present invention comprises a plurality of spaced multi-wall construction units as shown in the drawings, arranged so as to form a deep water drilling and production platform designated generally A in FIG. 1. It will be appreciated that the construction units may be formed into various other configurations of vessels and structures besides the drilling platform shown without departing from the present invention.

As shown in FIG. 1, the drilling and production platform A is positioned with its base B embedded in the ocean floor F with a work and storage platform P supported above the surface of the water W by means of a longitudinally extending stern S which extends upwardlyfromthebaseRBetweenthebaseBandthe stem S is an underwater work and storage chamber C for storing oil produced from the production platform and also providing an underwater work area. A drilling derrick D is shown rotatably mounted on the platform P for conducting drilling operations from such platform through the stern S and a rotatable wave guard G is mounted on the stern S below the platform P for protecting the drilling platform from ice or high waves.

Considering now the apparatus of the present invention in more detail, the sidewalls of the base portion B, the storage chamber C and the stern S are formed of a plurality of laterally spaced multi-wall construction units of the present invention.

As best seen in FIG. 2 of the drawings, the construction units forming the base portion B comprise inner and outer cylindrical sidewalls 11 and 12, respectively, which are laterally spaced relative to each other and which are supported in such laterally spaced relationship by an upper transverse plate 14 and a lower U- shaped transverse plate or member 15. Such members may be welded or otherwise suitably secured to the laterally spaced walls or inner and outer skin 11 and 12, respectively. A hemispherical bottom closure 17 comprises a spaced inner wall 170 and an outer wall 17b with a space 17c therebetween. Such walls 17a and 17b are secured to the inner wall 11 near its lower edge by welding or other suitable means to provide a lower closure for the base B.

A dredge or conduit 20 is provided below the hernispherical bottom 17 for removing mud or sand or silt from beneath the base B and filling the excavated area with concrete or other stabilizing material for supporting the drilling and production platform A thereon. Such conduit 20 comprises a central conical member having a plurality of laterally extending conduits 21 circumferentially spaced therearound and projecting outwardly therefrom through which sand or silt can be removed from the ocean floor F beneath the hemispherical bottom 17 by a suitable dredging apparatus (not shown) and through which stabilizing material such as concrete 22 or other suitable material can be injected to the excavated area. As shown, openings 17d are provided near the top of the hemispherical members 17a and 17b through which the upper end of the conduit 20 extends. it will be appreciated that suitable conductor pipes (not shown) can be connected to the conduits 21 for conducting excavated material to the surface or for discharging it onto the ocean floor near the platform base B as well as for conducting stabilizing material or fill to the excavated area from the drilling platform P at the surface of the water.

A plurality of circumferentially spaced openings We are provided in the hemispherical shell or plates 17a and 17b for receiving conductor guides 23 through which drilling and production pipes extend as will be described in detail hereinafter. Blow out preventers 230 are preferably provided on the conductor pipes 23.

As best seen in FIG. 3 of the drawings, the inner and outer skins 11 and 12 are spaced radially apart by a plurality of radially extending plate separators which connect the laterally spaced cylindrical walls forming the base B at circumferentially spaced points. A construction unit preferably comprises a wall section including a pair of adjacent plate separators 30 and the inner and outer skins 11 and 12 extending between such adjacent plate separators. The skins 11 and 12 may be formed on a continuous strip or of a plurality of sections, and depending on the height of the individual unit, may include a plurality of strips placed one above the other.

Such units are provided with circumferentially extending tension means for imposing a tension prestress on the separator plates 30. in the preferred form of this invention, such tension means include tension bars and 36 whose outer ends are welded to adjacent plates 30 and whose inner adjacent ends are threaded to receive turnbuckles 38 to impose the desired amount of tension on the separator plates to which the opposite ends of such bars 35 and 36 are secured. Such bars may either be welded to the separator plates 30 or may extend through suitable openings through such plates and be secured by means of a nut or other securing device attached to the ends of the rods 35 and 36, respectively.

As shown in FIG. 4 of the drawings, the plurality of substantially horizontal and parallel tensioning means 33 are positioned one above another and connect adjacent plate separators 30 so as to place then under tension. Similarly, the base B is provided with a plurality of substantially vertical tension means comprising rods or bars 41 and 42, with the upper end of rod 41 connected to the annular wall 14 and the lower end of rod 42 connected to the annular wall 15. The inner adjacent ends of the rods 41 and 42 are threaded to receive tumbuckles 44 which are provided for imposing tension on the plates 14 and 15, respectively. A manhole or other suitable opening 110 is provided in the inner wall to provide access for a workman to the area 31 between the walls 11 and 12 for tightening the tumbuckles 38 and 44, respectively. The outer ends of the rods 41 and 42 can be secured by welding or other suitable means to such annular walls 14 and 15, as desired.

Also, as shown in FIGS. 3 and 4 of the drawings, a plurality of diagonally extending braces 50 is provided on the inner skin 11 and a plurality of similar braces 51 is provided on the outer skin 12. Such braces 51 extend diagonally in an opposite direction to the braces 50. Such braces 50 and 51 are preferably longitudinally extending strips of angle iron having a pair of diverging legs such as 50a and 50b which are disposed at right angles to each other. The leg 50a is positioned adjacent to the inner skin 11 and welded or otherwise secured thereto with the leg 50b projecting toward the outer skin 12.

Similarly, the braces 51 comprise longitudinally extending right angle members having legs 51a and 51b which are disposed at substantially right angles relative to each other. As shown, the braces 51 are arranged with the legs 51a engaging the inner surface of the outer skin 12 and welded or otherwise secured thereto with the legs 51b projecting laterally inwardly toward the inner wall 11. The opposite ends of the braces 50 and 51 are connected by welds to the plate separators 30.

As best seen in FIGS. 4 and S of the drawings, transverse connecting means are provided at each intersection of the diagonal braces 50 and 51, respectively, for holding the skins 11 and 12 in laterally spaced relationship and to prevent buckling when tension is applied thereto. Such transverse connecting means comprises a longitudinally extending shaft or bolt 61 which extends through a suitable opening 62 in the inner skin 11 and also in the adjacent leg 50a and through a similar opening 63 that is formed in the outer skin 12 and in the adjacent brace leg 510. A nut 65 or other suitable securing means is provided on the end of threaded shaft or bolt 61 for securing the skins 11 and 12 and cross-braces S0 and 51, respectively, to the bolt 61.

A tubular stiffener 65 extends transversely between the adjacent legs 50a and 51a of the braces 50 and 51, respectively, and surrounds the shaft 61 which extends therethrough. As shown in FIG. 5 of the drawings, the angular braces 50 and 51 are arranged so that the inwardly projecting leg 50!: on the brace 50 is disposed on an opposite side of the tubular stiffener 65 from the angular leg 51b of the brace 51.

It will be appreciated that with the structure of the construction units of this invention as shown in the drawings, the horizontal rods 35 and 36, the vertical rods 41 and 42 and the transverse shafis or bolts 61 may each be individually tightened so as to prestress the construction unit prior to filling the area 31 between the walls 11 and 12 with concrete, aggregate, grout or the like. A valve 12a is connected to the outer wall 12 for filling the space 31 between the inner and outer skins 11 and 12 with concrete, etc.

It will also be appreciated that the preferred construction of the hemispherical base 17 is similar to the construction of the sides of the cylindrical base 8 in that similar tensioning means (not shown) are used in prestressing the bottom member 17.

A lower working platform or floor 70 is provided in the base B and extends transversely of the inner cylindrical wall or skin 11 and is welded or otherwise secured thereto. Such floor 70 is provided with openings 71 through which the conductor pipes or guides 23 extend.

An intermediate floor 73, which extends transversely of the base B adjacent the upper edge thereof, is welded or otherwise secured to the inner cylindrical wall 11 for supporting such floor 73 vertically above the floor 70. Suitable openings 74 are also provided in the floor 70 for receiving the conductor pipes 23. An opening 76 is provided for receiving the cylindrical elevator shaft 78 that extends upwardly from the floor 70 through the stem 8 to the work platform P above the surface of the water W. The floors 70 and 73 provide storage or working space for production and workover equipment or the like in the base B. The floors 70 and 73 each preferably comprise a plurality of sections 70a with an opening 70b therein for receiving a tubular conductor guide 23 which is normally disposed in such openings. A casing 76a is disposed in the tubular conductor guide 23 and, as shown in the drawings, receives the string of drill pipe 77 such as is used in rotary drilling of oil and gas wells and the like.

The storage body C which is positioned on the base B comprises a truncated cone which includes laterally spaced inner and outer skins or walls 80 and 81, respectively, which are spaced relative to each other so as to provide an opening 82 therebetween for receiving tensioning means as well as concrete, aggregate, grout or the like. A valve 810 is provided in the outer skin 81 for injecting concrete, grout, etc. into the space 82 between the walls 80 and 81. The structure of such conical storage member C includes longitudinally extending tensioning means 84 connecting the annular plate or member 14 at the lower edge of the spaced walls 80 and 81 with the stem attachment ring 85 which extends circumferentially of the stern S and secures such stem S to the upper end of the truncated conical storage section C as will be described in detail hereinafter. A manhole or other suitable opening 81a is provided in the inner skin 81 for providing access by a workman to the space 82 for tightening the tumbuckles (not shown) on the tensioning means 84.

In the preferred form of this invention, the inner and outer skins or laterally spaced walls 80 and 81, respectively, are each provided with diagonally extending angular braces (not shown) such as the braces 50 and 51 shown and described in connection with the cylindrical base portion B of this invention. The diagonal braces in the conical section C may not be positioned parallel to each other but instead, they are preferably arranged so that their adjacent upper ends are closer together at the top of the conical section C then their adjacent lower ends at the bottom of the conical section C. Additionally, the conical storage section C is preferably formed of a plurality of individual segments which include transversely extending plate separators (not shown) which connect such inner and outer conical walls and 81 at circumferentially spaced points to provide a plurality of structural segments for multi-wall construction units. Transverse tension means (not shown) is similar to the transverse tension means 60 and are provided at spaced intervals around the inclined walls 80 and 81, respectively. Thus, it will be appreciated that although the inclined walls 80 and 81 form a conical housing C rather than a cylindrical housing such as the case with the base B, such conical housing is divided into a plurality of segment sections or construction units suitable for pre-fabrication prior to final assembly and that such construction units can be pre-tensioned after final assembly by tightening the tensioning means provided therein.

A plurality of storage compartments are provided in the conical storage housing C for storing oil or other material, as desired. Such compartments 90 are formed by a plurality of vertically spaced inplined plates which extend radially outwardly from adjacent the cylindrical elevator shaft 78 to the inner skin or wall 80. Support rings 72 are welded or otherwise secured to the cylindrical shaft 78 at longitudinally spaced intervals for receiving the inner edges 91a of the inclined plates 91 forming the storage compartments 90. Each of such plates 91 is provided with suitable openings 94 for receiving the conductor guides 23.

Below the storage compartments 90 are a pair of storage areas or work areas 96 and 97 formed in the conical member C by means of substantially horizontally extending plates 98. These areas may be used for work or storage areas, as desired. An opening 98a is provided in the plate 98 for receiving a cylindrical elevator shaft 78 and openings 98b are provided for receiving the conductor guides 23.

As illustrated schematically in FIG. 2, an elevator 100 is positioned in the central shafl 78. Such elevator may be suspended by a cable 102 which extends upwardly through the shaft 78 to a suitable lifting and lowering means (not shown) preferably located on the drilling platform P for operating the elevator 100.

The stem S which extends upwardly from the top of the conical storage chamber C for supporting the drilling platform P above the surface of the water W is preferably a cylindrical structure formed in substantially the same manner as the laterally spaced multiwall construction of the cylindrical base B, including inner and outer skins and 111, which are provided with a lattice type network of supporting beams (not shown) similar to the diagonal supports 50 and 51 as well as transverse tension means, vertical, longitudinal and circumferential tension means for prestressing the stem structure prior to filling the area between the inner and outer skins 110 and 111, respectively, with concrete, grout or other suitable material.

As shown in P16. 2 of the drawings, the stem connecting ring 85 comprises an outer cylindrical housing having an inner surface 85a tapered inwardly and downwardly forming an inverted conical recess for receiving an inner ring or stem base 86 which comprises a ring having an inwardly and downwardly tapered surface 860 having a generally conical configuration which is received in the inverted conical depression 85a in the outer connecting ring 85. Such inner ring 86 is also provided with an upper inclined or tapered shoulder 87 which is inclined inwardly and upwardly for receiving a lock ring 88 which is normally seated on the annular shoulder 85b of the cylindrical housing 85. Such lock ring 88 is provided with an outwardly and downwardly inclined surface 884 which is inclined at substantially the same angle as the surface 87. Such lock ring 88 is provided with a plurality of circumferentially spaced openings for receiving locking bolts 89 which are provided for securing such lock ring to the connecting ring 85. A plurality of circumferentially spaced openings 86b extend through the rings 85 and 86 for receiving the conductor tubes 23 which extend downwardly through the stem S from the platform P.

Such drilling platform P is supported at the upper end of the stem S by a plurality of braces 120 which extend upwardly from a supporting ring 121 to the base 122 of such platform P. The drilling ring D is shown positioned eccentrically of the stem S and the upper portion 125 of such platform P which rotatably supports the derrick D with regard to the base 122 so as to permit the drill pipe D that is supported in the derrick D to be aligned with each of the circumferentially arranged conductor guides 23 that are circumferentially spaced in the stern S. Thus, it will be appreciated that drilling operations may be conducted through one of such circumferentially disposed conductor guides 23 and after such operations have been completed, the upper portion 125 of the platform P may be rotated to thus align the derrick D above another of the circumferentially spaced conductor guides 23 for further drilling or reworking operations. Also, in the preferred form of this invention, the derrick D comprises a hexagonal derrick having a total of six legs rather than a conventional derrick having only four legs.

Thus, in using the spaced multi-wall construction unit of the present invention for constructing a deep water drilling and production vessel or platform, a plurality of prefabricated construction units or segments of the structure may be shop fabricated and thereafter assembled in a drydock facility so as to form the cylindrical base portion B, the conical storage chamber C and the stern S which projects vertically above the top of the conical storage section C and thereafter the entire structure may be floated to the particular location at which it is to be erected and after being prestressed so as to place the inner and outer skins and the plate separators in tension to the desired amount, the space between the inner and outer skins may be then filled with concrete, aggregate, grout or other suitable substantially incompressible material which will cause the base portion of the structure to sink to the bottom of the ocean. The area immediately beneath the bottom B can then be excavated by means of a dredge apparatus connected through the conduits 21 to thereby sink the bottom of the base 8 into the ocean floor F. With the structure thus positioned the excavated area beneath the hemispherical bottom closure 17 can then be filled with cement or grout or other stabilizing material pumping such material through the conduits 21 to provide a stable bottom for the base B. It will be appreciated that with suitable ground anchors in position for adding further support and stability to the apparatus A, that then drilling operations may be conducted through the plurality of circumferentially spaced conductor guides 23. As drilling proceeds, casing 760 can be set in each of the holes drilled through such guides and, in the event production is obtained, oil or molten sulphur or other material may be stored in the various storage compartments in the storage housing C until it is desired to transport such material to shore.

Also, it will be appreciated that the spaced multiwall construction unit of the present invention may be employed for constructing other types of structures that are subjected to high internal and/or external pressure in a plurality of pre-fabricated units which are lightweight and relatively easily transportable. Such construction units can be pd after final assembly and then filled with aggregate, concrete or other suitable material to form a rigid pressure vessel structure.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

I claim:

1. A spaced multi-wall construction unit for constructing vessels or structures subjected to high internal or external pressures comprising:

a. a plurality of laterally spaced walls positioned side by side;

b. an upper transversely extending member connecting the adjacent upper edges of said laterally spaced walls, a lower transversely extending member connecting the adjacent lower edges of said laterally spaced walls and a pair of transversely extending side members connecting the adjacent side edges, respectively, of said .walls to form an enclosure; and

. first tension means connecting said upper and lower transverse members and second tension means connecting said pair of transversely extending side members to tension said multi-wall construction unit.

2. The apparatus of claim 1 including a substantially incompressible material disposed in the space between said laterally spaced walls to form a rigid construction unit.

3. The apparatus of claim 1 including a plurality of radially extending tension bars connecting said laterally spaced walls.

4. The invention of claim 3 wherein said radially extending tension means includes means extending radially from one of said walls to another of said walls to prevent buckling thereof including a longitudinally extending shaft extending through said walls, a tubular stiffener surrounding said shaft and means for adjusting the length of said shaft for securing said walls to said buckle resistant means.

9 The apparatus of claim 1 wherein said tension means are adjustable to permit the desired amount of tension to be imposed on said construction units.

A spaced multi-wall consu-uction for constructing vessels or strucmres subjected to high internal or external pressure comprising:

a plurality by side; an upper transversely extending member connecting the adjacent upper edges of said laterally spaced walls, a lower transversely extending member connecting the adjacent lower edges of said laterally spaced walls and a pair of transversely extending side members connecting the adjacent side edges, respectively of said walls to fonn an enclosure; and

of laterally spaced walls positioned side The invention of claim 6 wherein said longitudinally extending braces comprise angle straps having a pair one of said walls and the other leg toward the other wall.

of divergent legs, one of said legs being secured to projecting laterally a n a a. 

1. A spaced multi-wall construction unit for constructing vessels or structures subjected to high internal or external pressures comprising: a. a plurality of laterally spaced walls positioned side by side; b. an upper transversely extending member connecting the adjacent upper edges of said laterally spaced walls, a lower transversely extending member connecting the adjacent lower edges of said laterally spaced walls and a pair of transversely extending side members connecting the adjacent side edges, respectively, of said walls to form an enclosure; and c. first tension means connecting said upper and lower transverse members and second tension means connecting said pair of transversely extending side members to tension said multi-wall construction unit.
 2. The apparatus of claim 1 including a substantially incompressible material disposed in the space between said laterally spaced walls to form a rigid construction unit.
 3. The apparatus of claim 1 including a plurality of radially extending tension bars connecting said laterally spaced walls.
 4. The invention of claim 3 wherein said radially extending tension means includes means extending radially from one of said walls to another of said walls to prevent buckling thereof including a longitudinally extending shaft extending throUgh said walls, a tubular stiffener surrounding said shaft and means for adjusting the length of said shaft for securing said walls to said buckle resistant means.
 5. The apparatus of claim 1 wherein said tension means are adjustable to permit the desired amount of tension to be imposed on said construction units.
 6. A spaced multi-wall construction for constructing vessels or structures subjected to high internal or external pressure comprising: a. a plurality of laterally spaced walls positioned side by side; b. an upper transversely extending member connecting the adjacent upper edges of said laterally spaced walls, a lower transversely extending member connecting the adjacent lower edges of said laterally spaced walls and a pair of transversely extending side members connecting the adjacent side edges, respectively of said walls to form an enclosure; and c. first tension means connecting said upper and lower transverse members and second tension means connecting said pair of transversely extending side members to tension said multi-wall construction unit with longitudinally extending braces secured to one wall and extending diagonally in one direction with longitudinally extending braces secured to the other wall and extending diagonally in another direction.
 7. The invention of claim 6 wherein said longitudinally extending braces comprise angle straps having a pair of divergent legs, one of said legs being secured to one of said walls and the other leg projecting laterally toward the other wall. 